The present application is a 371 of International Patent Application No. PCT/AU98/00989, filed Nov. 30, 1998, which claims priority to Australian Patent Application No. PP 0694, filed Dec. 1, 1997.
THIS INVENTION relates to a curtain assembly for waste treatment which may be utilized for treatment of wastes, which include faeces from animals inclusive of piggeries, stockyards, cattle feedlots and the like, wastes from breweries, distilleries and fermentation processes and any other waste which may be metabolized by micro-organisms.
Reference may be made to International Publication W092/11210 which refers to treatment of wastes also utilizing a curtain assembly. In this prior art specification, there is described a process for treatment of biological waste which included the step of passing liquid waste downwardly through a substantially vertically orientated curtain formed of flexible reticulated cellular material, such as reticulated polyurethane foam, bonded to a reinforcing nylon cloth core. The curtains at laboratory scale were 2 m long and 0.1 m wide and liquid waste was pumped to the top of the curtain and subsequently trickled down through the curtain which had been previously inoculated with micro-organisms such as Candida ingens and Geotrichum fragrans. Such micro-organisms were pellicle-forming oxidative organisms which were able to obtain their oxygen directly from the atmosphere as described in Henry et al., 1983, European J. Appl. Microbiol. Biotechnol. 18 109-113.
The process of W092/11210 was efficacious in use and could be utilized for treatment of a wide variety of waste as described above and, in particular, strong waste which is generated by commercial enterprises, such as breweries, distilleries and piggeries, milk processing and grease trap waste treatment centres.
However, it has now been found in practice that the use of flexible reticulated polyurethane foam for waste treatment as described above was unsatisfactory and had certain disadvantages. One disadvantage was that very finely divided particulate matter or silt, which was derived from lignocellulose, tended to collect within the cells of the polyurethane foam and filled up the cells denying the filamentous micro-organisms access to atmospheric oxygen which was essential to the effective cultivation of such micro-organisms. Such silt also reduced the effective surface area of the foam which could be occupied by the micro-organism. It was therefore frequently necessary to wash the fine silt off the polyurethane foam and this disrupted commercial operation of the polyurethane foam as it was then necessary to reinoculate the curtain with the filamentous micro-organism.
Another disadvantage in relation to reticulated polyurethane foam was that such foam was frequently used by flies of the family Psychodidae, alternatively known as xe2x80x9cmoth wing fliesxe2x80x9d to lay their eggs and the resulting larvae also disrupted satisfactory use of the polyurethane foam as a waste treatment curtain.
It therefore is an object of the invention to provide waste treatment apparatus and a method of waste treatment using a curtain assembly to alleviate one or more of the aforementioned disadvantages.
The invention, therefore, in one aspect, provides a method of waste treatment which includes the steps of:
(i) inoculating one or more vertically oriented curtains formed of mesh material having a minimal aperture size of 0.1-5.0 mm with micro-organisms which are pellicle forming oxidative organisms so as to form a microbial lawn or mat adhering to the curtain;
(ii) passing waste liquid downwardly through the curtain; and
(iii) collecting treated waste liquid below the curtain.
The invention, in another aspect, refers to a waste treatment apparatus including:
(i) one or more vertically oriented curtains each formed of flexible mesh material having an aperture size of 0.1-5.0 mm;
(ii) means for applying liquid waste to said curtain(s) located above said curtain; and
(iii) collection means for collection of treated waste after passage through said one or more curtains.
The aperture size of the mesh is critical to the successful performance of the invention and depends upon a unique relationship between pellicle forming micro-organisms, the stream of waste liquid passing down the mesh on both sides thereof and the degree of oxygen access to the pellicle formers. If the aperture size is too small, i.e. less than 0.1 mm, then the pellicle formers will not grow successfully because of insufficient oxygen access and if the aperture size is too large, i.e. greater than 5 mm, then the pellicle formers will tend to have difficulty in forming a lawn and fall off the curtain. The mesh material may comprise knitted, woven or knotted fabric with open spaces between threads of the fabric which have the aforementioned aperture sizes.
However, it will also be appreciated that the mesh may also be formed from non-woven material or have any structure formed by intersection of threads running in one direction (i.e. xe2x80x9cwarpxe2x80x9d threads) and threads running in another direction normal to the first direction (i.e. xe2x80x9cweftxe2x80x9d threads). However, it will be appreciated that the mesh threads can have any suitable pattern of intersection and thus form apertures or open spaces of rectangular, square, diamond shape, polygonal shape or even triangular shape.
Preferably, the mesh material is formed from commercial shadecloth obtainable, for example, under the trade marks xe2x80x9cWEATHAMESHxe2x80x9d, xe2x80x9cGEOTEXxe2x80x9d and xe2x80x9cSARLONxe2x80x9d and may have product specifications having 50-90% UV cover factor. Usually shadecloth is obtainable commercially having a width of 1.83-3.66 m and other specifications may include weight of between 98-231 gms/m2, courses per inch of between 8.5-20 and wales per inch of 6.25. Usually such shade cloth is formed from polymeric material.
A particularly preferred form of shadecloth used for Examples 1-4 hereinafter was xe2x80x9cWEATHASHADExe2x80x9d shadecloth having 69.2% UV cover factor, 226 gms/m2, 20 courses per inch, 6.25 wales per inch and 3.66 m wide.
The method of the invention suitably utilizes a curtain assembly comprising one, but more preferably, an array of spaced curtains which may be separated by a spacing of between 30-100 mm. Each curtain may be suspended by a support which may be of any suitable type but which may comprise a plurality of spaced bars oriented in a horizontal plane wherein a length of curtain is draped over an adjacent bar. However, it will be appreciated that any other support may be utilized, such as a support frame or support plate having spaced slots for supporting an individual curtain.
Preferably, each curtain in a curtain array is spaced from each other by spacing means, such as individual spacers, which retain each curtain in a fixed orientation so as to maintain the aforementioned spacing of 30-100 mm. Such spacers may be of any suitable type and comprise, for example, tubes or rods which are attached to a common support, such as a cord or wire.
It is also preferred that each curtain be tensioned adjacent a bottom edge so as to maintain each curtain in a taut and substantially planar condition. One form of tensioning means may include clamps which clamp each of the bottom edges of a respective curtain to an adjacent support. Alternatively, and more preferably, each of the curtains has a tie which is looped around or attached to a support. The tie may be attached to an adjacent curtain in any suitable manner, such as by passing through apertures in the curtain.
The waste to be treated by the method of the invention is suitably transported to the top of the curtain assembly by an inlet conduit or conduits by a pump of suitable type and be applied to the top of the curtains in the form of a jet or pressurized spray. The waste, in the form of a liquid (which term also includes xe2x80x9cslurryxe2x80x9d or xe2x80x9csuspensionxe2x80x9d) may subsequently percolate down the curtain through the thick microbial lawn of micro-organisms.
It is also found efficacious in the method of the invention that pressurized air is passed horizontally between adjacent curtains which may be heated to a suitable cultivation temperature for propagation of the micro-organisms which may comprise from 28-42xc2x0 C. and, more suitably, 32xc2x0 C. Such pressurized air may be applied from an inlet manifold having a plurality of spaced ports and be received by an exhaust manifold also having a plurality of spaced exhaust ports. Suitably, the pressurized air is applied along the height of each of the curtains in a particular array.
Preferably, each array of curtains is accommodated within a housing which may be provided with an inlet through which the inlet conduit(s) transporting waste may project. Preferably, the or each inlet conduit may have a nozzle or jet to apply the waste in a spray to the curtain array wherein the spray may be entrained with solid particulate waste.
In a preferred embodiment, there may be a plurality of housings which are spaced from each other whereby waste may be transferred sequentially from a first housing and then through one or more intermediate housings and lastly through a final housing. In this embodiment, each of the housings may have a suitable collection means in the form of a collection compartment or drainage compartment which are each preferably arranged on a slope or at successively lower heights so that liquid waste in one drainage compartment may then be transferred to an adjacent housing by gravity. Each of the housings may be provided with inlet conduits for circulation of waste as well as suitable outlet or drain conduits.